Martian moon may have come from impact on home planet

The dark faces of the moons resemble the primitive asteroids of the outer solar system, suggesting the moons might be asteroids caught long ago in Mars' gravitational pull. But the shapes and angles of the moons' orbits do not fit this capture scenario.

A fresh look at 20-year-old data from the Mars Global Surveyor mission lends support to the idea the moons of Mars formed after a large impact on the planet threw a lot of rock into orbit, according to a new study in the Journal of Geophysical Research: Planets, a publication of the American Geophysical Union.

Dataset - Clues - Stuff - Phobos - Crust

The dataset held unplumbed clues to the stuff Phobos is made of, which may be more similar to the crust of the Red Planet than it appears, according to the study's authors.

"The fun part for me has been taking a poke at some of the ideas out there using an old dataset that's has been underutilized," said Tim Glotch, a geoscientist at Stony Brook University in New York and the lead author of the new study.

Marc - Fries - Scientists - Curator - Dust

Marc Fries, a planetary scientists and curator of cosmic dust at NASA's Johnson Space Center, who was not involved in the new study, said the inability to explain the genesis of two moons around a neighboring planet is a glaring shortcoming in scientists' understanding of moon formation. Clearing it up will help with interpretations of how other moons and planets formed in our solar system and beyond. The new study does not clinch the mystery, but it is a step in the right direction, he said.

"The issue of the origins of Phobos and Deimos is a fun sort of mystery, because we have two competing hypotheses that cannot both be true," Fries said. "I would not consider this to be a final solution to the mystery of the moons'...